SYNTHESIS, CHARACTERIZATION AND REACTIVITY OF OXOMOLYBDENUM(V) COMPLEXES WITH ONS AND NNS DONORS

The monomeric oxomolybdenum(V) complexes, [MoOLCl(2)] <(1a)under bar>- <(1d)under bar> [HL=S-benzyl/methyl 3-(2-pyridyl)methylenedithiocarbaz ate (<(1a)under bar> and (1) under bar), or N-methyl-S-benzyl/methyl 3 -(2-hydroxyphenyl)methylenedithiocarbaz (<(1c)under bar> and <(1d)unde r bar>) are synthesized by the reaction of MoOCl52- with HL ligands. A ll these complexes show magnetic moment of about 1.7B.M. The complexes , <(1a)under bar> and <(1b)under bar> exhibit rhombic g-tensor anisotr opy (like xanthine oxidase) whilst <(1c)under bar> and <(1d)under bar> show axial spectrum. The above complexes undergo irreversible electro chemical reduction furnishing Mo(IV) species and the potentials are de pendent on the S-substituents. Reactions of MoOX(5)(2-) (X = Cl or Br) with H(2)L(1) [H(2)L(1) = S-methyl 3-(5-R-2-hydroxyphenyl) methylened ithiocarbazate] (R=H, CH3, Cl, Br) produce complexes of thiolatobridge d dimers, [Mo(2)O(2)L(2)(1)X(2)], which show sub-normal magnetic momen ts at room temperature. The metal-centred irreversible oxidation and r eduction of these complexes show expected dependence on the R-substitu ents of the salicyl phenyl ring of the ligands.